The invention relates to an injection device of the single-use type, which is designed to be pre-filled with a dose of liquid, in particular a medicinal liquid, to be injected.
Single-use injection devices which are designed to be pre-filled comprise a syringe body, which is either provided with a base, in which there is sealed a needle, which is protected by a protective cap, or comprise a conical male locking connection, which makes it possible to fit onto the said syringe body a conical female locking connection, which supports an injection needle protected by a protective cap, the said conical connections defining an assembly which is commonly known as a xe2x80x9cLxc3x9cER conical assemblyxe2x80x9d.
The most conventional injection devices, known as the xe2x80x9cwet needlexe2x80x9d type, are of the type provided with a syringe body comprising a base, in which there is sealed an injection needle, which is closed off by means of a protective elastomer cap, which is provided with a inner blind bore contained in the base of the said cap, inside which the end of the said needle is forced, such as to guarantee the sealing of the injection device before injection takes place.
The first disadvantage of injection devices of this type consists in the fact that when the protective cap is put into place, the injection needle must be centred perfectly in relation to the bore in the said cap. However, in practice, this centring is sometimes approximate, such that fitting of the cap frequently leads to deterioration of the said cap or needle, resulting in significant numbers of production rejects.
In addition, according to this principle, the quality of the needle (sharpness, silicone coating), is systematically affected by the occurrence of friction of the point of the said needle against the inner wall of the blind bore in the cap, when the latter is forced on.
Finally, the liquid contained in these injection devices is necessarily in contact with the materials which constitute the injection needle and the protective cap, which, for certain types of liquid, can affect the conservation of the latter.
In order to eliminate these disadvantages, numerous injection devices known as the xe2x80x9cdry needlexe2x80x9d type have been designed, wherein the injection needle is isolated from the liquid contained in the syringe body until the moment of injection.
A first type of xe2x80x9cdry needlexe2x80x9d injection device is that which is commonly used in dentistry, and comprises a bottle, which contains the liquid to be injected, and is closed off by a membrane, and a double-point needle, which can be displaced axially relative to the said bottle, such as to pierce the membrane at the moment of injection. Injection devices of this type are described in particular in patents DE-847473, FR-2347055, U.S. Pat. No. 4,639,250, EP-602883, DE-2008751, DE-1909794.
This type of injection device has two sorts of disadvantages. In fact, firstly, the fact of needing a double-point needle leads to a increase in the cost price of these injection devices, derived firstly from the cost of the said needle itself, and secondly from the necessity of carrying out two sharpening operations instead of a single sharpening operation required for a conventional needle. In addition, for needles with a small diameter, it often happens that problems of coring arise, leading to the inclusion of particles of membrane inside the aperture of the needle, which either close off this aperture, or are injected together with the liquid.
A second type of xe2x80x9cdry needlexe2x80x9d injection device comprises a syringe body which accommodates two stoppers, which delimit the chamber containing the liquid, and onto which a base is crimped, the said syringe body additionally having a compartment which is provided with a duct for communication with the injection needle, which is disposed such as to be put into contact with the chamber only after the pistons have been displaced axially.
Injection devices of this type, which are described in particular in patents FR-2412320, FR-2208684, EP-191508, EP-588148 and EP-720857, make it possible to eliminate the disadvantages of the above-described injection devices. However, they themselves also have two disadvantages. In fact, firstly, the operation of crimping the base onto the syringe body is problematic, and requires particular care in order to guarantee perfect sealing between the said base and the said syringe body. In addition, and above all, injection devices of this type can be subject to accidental escape of the liquid contained in the chamber, resulting for example from expansion of the volume of gas contained in the said chamber, or from depressurisation, in particular during transport by air, which lead to axial displacement of the stopper for access to the compartment for discharge of the liquid.
A third type of xe2x80x9cdry needlexe2x80x9d injection device, described in particular in patents EP-150681, EP-111796, FR-2330413 and WO-8404252, makes it possible to eliminate all of the above-described disadvantages. For this purpose, these injection devices comprise firstly a syringe body, which is provided with a chamber closed off by a rubber stopper, which contains a longitudinal through-bore, and secondly, a base which is mobile axially inside the bore of the said stopper, and is provided with ducts which are disposed such as to put the injection needle and the chamber into communication during axial displacement of the said base, which tends to thrust the latter into the stopper.
The invention relates to an injection device which has a design similar to that of the injection devices of the third type described above, and the main objective of which is to provide an ergonomic injection device, which combines the advantages of these injection devices (sealing, guarantee against risks of accidental escape, etc), the activation of which for the purpose of an injection is carried out very simply, by means of a very natural gesture.
For this purpose, the invention relates to an injection device comprising a syringe body, which delimits a chamber which is designed to be filled with a liquid, in particular a medicinal liquid, and a unit for closing off the chamber and distributing the liquid, comprising an end piece for closing off the said chamber, which is firstly extended by a base, in which there is sealed a needle which is covered by a protective cap, and secondly, which is perforated in the extension of the said needle by a duct for distribution of the liquid, the said unit for closing off and distributing being mobile axially between a position known as the closing-off position, in which the distribution duct is isolated from the chamber of the syringe body, and a position known as the injection position, in which the said distribution duct communicates with the said chamber.
According to the invention, this injection device is characterised in that:
the unit for closing off and distributing comprises an intermediate section, which is disposed between the closing-off end piece and the base, and is placed such as to extend in the extension of the syringe body;
the syringe body comprises a ring which is provided with a front wall, in which there is provided an axial opening for passage of the protective cap, and which delimits two inner compartments which are juxtaposed axially, each of which has a shape which is conjugated with the intermediate section of the unit for closing off and distributing, and can accommodate the said intermediate section, the said compartments being separated by axial stop units which can permit axial displacement of the intermediate section of one compartment towards the other compartment;
the ring and the intermediate section comprise respectively inner and outer conjugated units, for relative locking in rotation of the said ring and intermediate section;
the cap comprises an end section, which is designed to extend through the axial opening of the front wall of the ring, such as to cover the base and abut axially the intermediate section of the unit for closing off and distributing;
the end section of the cap, and the intermediate section of the unit for closing off and distributing have at the front, and opposite, conjugated profiles in the form of a cam, which can give rise to axial displacement of the unit for closing off and distributing, from its closing-off position towards its injection position, during movement of rotation of the protective cap; and
the cap comprises outer units which are designed to abut axially the front wall of the ring, in a position in which the said cap covers the base of the unit for closing off and distributing.
The activation of an injection device of this type, for the purpose of the injection, is thus derived from simple rotation of the protective cap, which gives rise to axial displacement of the unit for closing off and distributing, which brings the needle and the chamber of the syringe body into communication.
This activation thus simply requires performance of a natural movement, which is carried out conventionally, in order to remove a protective cap, consisting of imparting movement of rotation to the said protective cap.
In addition, the axial displacement of the unit for closing off and distributing which is generated by this rotation of the protective cap is irreversible, owing to the fact that any further, inverse displacement, is subsequently prevented.
According to another characteristic of the invention, each profile in the form of a cam has two slopes, which extend symmetrically on both sides of a longitudinal axis of symmetry, such as to permit rotation of the protective cap in either direction of rotation.
Thus, the activation of the injection device can be obtained equally well by turning the protective cap in either direction of rotation.
According to another characteristic of the invention, the profiles in the form of a cam, of the intermediate section of the unit for closing off and distributing, and of the end section of the protective cap, have respectively a conjugated concave shape and a convex shape.
According to another characteristic of the invention, the end section of the protective cap comprises a radial outer pin at the level of at least one of the profiles in the form of a cam.
In addition, for each outer pin of the protective cap, the ring then comprises a cutout provided in the periphery of the axial opening of the front wall, the said cutout being provided such as to be offset angularly by an angle (xcex1) relative to the outer pin, in the closing-off position of the unit for closing off and distributing, and to be plumb with the said outer pin in the injection position of the said unit for closing off and distributing.
According to this arrangement, the protective cap cannot be removed without firstly having undergone a movement of rotation, which makes it possible to bring each outer pin plumb with a cutout provided in the front wall of the ring, during which movement of rotation, as previously stated, the unit for closing off and distributing is automatically displaced axially.
The movement to be imparted to the protective cap in order to remove the latter thus corresponds exactly to the conventional movement imparted to any protective cap in order to remove it, i.e. a movement of rotation, combined with a traction force exerted on the said protective cap.
According to another characteristic of the invention, for each cutout in the front wall of the ring, the protective cap comprises a longitudinal fin, which is offset angularly by an angle (xcex1) relative to each outer pin of the said protective cap, which can slide in the said cutout when this protective cap is presented opposite the interior of the ring.
The presence of this (or these) fin(s) makes it possible to assemble the unit for closing off and distributing/and the protective cap/in a preceding step, then to fit the assembly by introducing it inside the ring, during which assembly the angular position of each outer pin of the cap is automatically indexed by means of the arrangement of the said fin(s).
In addition, and preferably, each longitudinal fin of the protective cap is interrupted at a distance from the end of the end section of the said protective cap, and has a thickness which is designed to abut axially the front wall of the ring.
In addition, according to another characteristic of the invention, each fin of the protective cap comprises a lateral outer surface which is inclined longitudinally, such as to form a ramp, which can allow the said fin to clear the cutout in the front wall of the ring, on completion of introduction of the said protective cap inside the said ring.
This form of the fins makes it possible to fit the closing-off and distributing unit/protective cap assembly inside the ring as previously described, whilst imparting to the said fins the function of an axial stop for the said protective cap on the front wall of the ring, once this assembly has been completed.
According to another characteristic of the invention:
the ring of the syringe body delimits an inner receptacle which has a cylindrical shape, and comprises at least one longitudinal inner groove, relative to the base of which there projects a catch, provided in an intermediate position along the said groove, which catch has longitudinally an outer surface in the form of a dihedron, which can act as an axial stop unit separating the two inner compartments of the said ring;
for each groove in the ring, the intermediate section of the unit for closing off and distributing comprises a lateral lug, which can be accommodated in the said groove, and has a shape which is conjugated with the compartments delimited by the catch which extends in the latter.
Additionally, the injection device according to the invention advantageously comprises a closing-off stopper with dimensions which are suitable for being inserted in the syringe body, provided with a through bore which opens into the said syringe body at a countersink.
In addition, in this case, the unit for closing off and distributing has dimensions which are designed to be inserted in the bore in the closing-off stopper, and comprises a distribution duct containing a transverse branch, which is disposed such as to be positioned recessed from the countersink in the said closing-off stopper, in the closing-off position of the unit for closing off and distributing, and to extend into the said countersink, in the injection position of the said unit.